WASHINGTON — Going to bat for confused passengers, the government is proposing that airlines be required to disclose fees for basic items such as checked bags, assigned seats and carry-on bags so consumers know the true cost of flying.

Under new regulations proposed Wednesday by the Transportation Department, detailed fee information — including for a first and second checked bag — would have to be provided wherever passengers buy tickets, whether online, on the phone or in person. Any frequent-flier privileges would also be factored into the price.